This document discusses hypersensitivity, classifying it into four types based on mechanisms. Type 1 is anaphylaxis caused by IgE antibodies binding to mast cells. Type 2 is antibody-dependent cytotoxicity. Type 3 involves immune complex deposition in tissues. Type 4 is cell-mediated delayed hypersensitivity. The types are distinguished by their pathophysiology and examples are given of conditions that fall under each type along with associated symptoms and treatments.

1. HYPERSENSITIVITY
BY
V NAVEEN SAHITH
MSc MICROBIOLOGY

2. INTRODUCTION
CLASSIFICATION
SYMPTOMS
PREVENTION AND TREATMENT

3.  INTRODUCTION
• Hypersensitivity is the violent reaction of the
Immune system leading to severe symptoms and
even death.
• Immune response is always directed towards
protect the human body. But in hypersensitivity
the immune response become dangerous to human
• Hypersensitivity can bring it’s symptoms either
immediately with in minutes or in delayed state
after 24 to 48 hours

4.  CLASSIFICATION
• P.G.H.Gell and R.R.A. Coombs proposed a
Classification scheme in which Hypersensitivity
reaction are divided into 4 types on the basis of
mechanisms
H.Type -1 (Antibody –mediated)
H.Type -2 (Antibody-mediated)
H.Type -3 (Immune complex- mediated)
H.Type -4 (Cell- mediated)

5.  Type -1 (Anaphylaxis)
•In type 1 hypersensitivity, B-cells are stimulated
(by CD4+TH2 cells) to produce IgE antibodies
specific to an antigen.
•This class of antibody high affinity to FC
receptors on the surface of tissue mast cells and
blood basophils.
•Mast cells and basophils coated by IgE
antibodies are “sensitized".

6. •

7. A later exposure to the same allergen cross- link
The membrane bound IgE on sensitized mast cells
and basophils causing degranulation

8.  SYMPTOMS:-
• Vasodilation
• Low blood pressure
• Swelling of throat and tounge
• Cardiac arrest leads to Death
• Hay fever

9.  TREATMENT:-
• Hyposensitivity(IgG)
• Stabilizing Mast cell – Isoprenaline, Sodium
chromoglycate
• Epinephrine

10.  Type -2 (Antybody - dependent)
• In type 2 Hypersensitivity is due to the
interaction of antibodies and cell associated
antigens
• When antibodies bind to antigens located on
surface of the cell become cytotoxic
• IgG Antibodies are involved in type 2
Hypersensitivity
eg:- Mismatch blood group transfusion
Erythroblastosis foetalis

12.  Type – 3 (Immune complex- mediated)
• The reaction of antibody with antigen
generates Immune complexes
• Generally this complexing of antigen with
antibody facilitates the clearance of antigen
by phagocytic cells. But However, Large
amount of Immune complexes can leads to
tissue damage

14.  SYMPTOMS:-
• Rheumatoid arthritis
• serum sickness
 TREATMENT:-
•Corticosteriods
• Antihistamine

15.  Type -4 (cell mediated)
• When some subpopulation of activated TH
cells encounter certain types of antigens.
This reaction leads to inflammatory reaction
cause tissue damage
• It is delayed type Hypersensitivity

17.  SYMPTOMS:-
• Local cell damage
• Inflammation
• Redness of skin
• Vesicle Eruption
 TREATMENT:-
• Corticosteroid

18.  Reference:-
• Immunology - Kuby
• Sara’s Immunology and microbiology